The present invention relates to a method of producing a plunger barrel and, in particular, a plunger barrel having a prestroke changing mechanism and which is used for a fuel injection pump in an internal-combustion engine.
A fuel injection pump in an internal-combustion engine is in general provided with a plunger barrel in which a plunger for transmitting fuel under pressure into a cylinder of an engine is accommodated. The plunger barrel has a sliding bore in which the plunger is slid, a control sleeve acceptor in the shape of a hole provided for the sliding bore and a window opened to a wall defining the acceptor hole, for example, as disclosed in Japanese Patent Laid-Open (KOKAI) 61-123756 (123756/1986).
In the conventional technology, when the plunger barrel of the kind described above is manufactured, the plunger barrel is manufactured by independently producing two parts, i.e., an upper flange portion and a lower barrel portion, with the control sleeve hole being a boundary, which are then integrated together through a cooling fit working and finally performing a finishing working, or is manufactured from a single shape member by first forming an outer shape of the plunger barrel and then forming the window through a machine working such as cutting working.
However, in the first method, it takes a long time to produce the plunger barrel and an increased number of processing steps is required because the flange portion and the barrel portion are to be independently manufactured. In the second method, the window opening is formed through the cut working, so that it takes a further longer time to produce the plunger barrel.